Hey, I'm sorry for coming back at you so late,
since they're CC0 licensed, you can do whatever you want with the models, even use them for commercial products and not give me any credit!
That being said, I'm afraid these might be too "heavy" for mobile games, sitting at 3000 quads each. That's why I deliberately called them Cartoon instead of Lowpoly. Maybe you can disable the interiors and make the windows opaque, that'll bring the polycount down to about 1000 each.
Have fun, and if you decide to use them, feel free to shoot me another comment (not mandatory, I'd just love to see these cars in action)!